There is a continuing search for cheaper and quicker analytical procedures. One way to accomplish this is to have an assay whereby two or more analytes can be assayed simultaneously in the same solution.
An example is in U.S. Pat. No. 4,146,602 issued on Mar. 27, 1979 which discloses a simultaneous assay of Folate and Vitamin B.sub.12.
Co.sup.57 is incorporated in Vitamin B.sub.12 which is rather uncomplicated since Vitamin B.sub.12 is a cobalt containing compound.
The problem was how to incorporate Co.sup.57 into noncobalt containing analytes.
The use of chelating agents is well known; however, there is no known use of chelating agents to prepare analytes useful in simultaneous assays.
A paper by Yeh et al. at pages 327-336 of J. Radioanal Chem., 53, (1979) describes the preparation of an assay of indium chelates. A chapter in the American Chemical Society publication Advances In Chemistry Series, No. 198 Modification of Proteins by Meares et al. at pages 360-387 discusses chelate tagged proteins and polypeptides using cobalt to prepare radiopharmaceuticals.
Egan et al at pages 611-613 of a paper entitled ".sup.57 Co: A Volume Mark for the TRIPLE-ISOTOPE, Double-Antibody Radioimmune Assay" in Immunochemistry, 1977, Vol. 14, discusses using a chelating agent (EDTA) with cobalt; but to prevent adsorption of cobalt to serum proteins.